Lithium batteries are widely used in consumer electronics industry due to their high energy density. Majority of the commercial batteries currently in use comprise a negative electrode material graphite along with one of a wide range of positive electrode materials such as lithium cobalt oxide (LiCoO2), lithium manganese oxide (LiMn2O4), lithium nickel oxide (LiNiO2), lithium nickel cobalt oxide (LiNiCoO2), lithium nickel cobalt manganese oxide (LiNiMnCoO2), lithium metal phosphate (LiMPO4), lithium nickel cobalt aluminum oxide (LiNiCoAlO2) and the like. More recently cell producers have started using high voltage materials like NMC and LMNO on the cathode side and high-energy silicon and tin based alloys or composites on anode side.
However, most of these cathode and anode materials still have limitations. For example, batteries employing lithium cobalt oxide (LiCoO2) use only 50% of the lithium during the charge/discharge process because the voltage is limited to about 4.2 Volt. Charging beyond 4.2 V, the crystal structure of the cell material destabilizes and further leads to self-destruction of the cell. Batteries incorporating lithium cobalt manganese nickel oxide composite material are known to potentially be one of the highest capacity materials, however the material tends to exhibit loss in voltage during repeated battery cycling which is a major drawback. In addition to the above said materials, spinel lithium manganese nickel oxide is another material with high voltage and high energy density. However due to manganese dissolution and other associated issues involved during the course of operation of the cell at high temperature the material performance is seriously harmed.
Besides the self-destruction of the cathodes during cell cycling (charging/discharging) occurs because the electrochemically active material has to sustain the mechanical strain and electrostatic forces while oscillating between different oxidation states, also causing a volume expansion and contraction of the crystallites during charge and discharge processes. Voltage and capacity fade during cycling or at high cell temperatures is one of the key deficiencies in these modern cathode materials. This also causes an electronic connection issue between electrode active particles with the binder as well as with the current collector.
With regard to the anode materials, silicon and tin are widely recognized for their desirable high volumetric and gravimetric capacities. These are much higher than graphite which is about 372 mAhr/g. For years, there has been a wide and well-funded effort to use silicon in rechargeable batteries as an anode material. Researchers have shown that silicon can deliver increased charging/discharging rates, specific capacity and increased power density, but suffer from poor cycle life which is the major limitation.
In the view of foregoing, there is an ongoing need for improved economic material, capable of storing high volume of lithium at high voltage and thereby providing a higher energy density and specific capacity than those now in use.